Interest-calculator



Patented Nov. 29, I898.

No. 6|4,8 5l.

w. DRAKE. INTEREST CALCULATOR.

(Application filed Nov. 8, 1897,)

3 sheets-sheet I.

{No Model.)

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Patented Nov. 29, I898. W. A-. DRAKE.

INTEREST CALCULATOR.

{Application filed Nov. 8, 1897.)

3 Sheets8heat 3 (No Model.)

UNITED STATES PATENT OFFICE.

\VARREN A. DRAKE, OF CHICAGO, ILLINOIS;

INTEREST-CALCUtATOR.

SPECIFICATION forming part of Letters Patent No. 614,851, dated November 29, 1898. Application filed November 8,1897. Serial No. 667,781. (No model.)

To on whom it may concern:

Be it known that I, WARREN A. DRAKE, of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Interest-Calculators, of which the following is a specification.

This invention relates to the provision of a labor-saving apparatus to be used in the calculation or computation of interest, annuities, &c. The prime factors in these computations are the principal, the time, and the rate, and the apparatus, by the aid of certain tables constructed upon the basis of a given rate of interest, enables the computation of interest upon various amounts or sums for various times, saving by its use numerous additions and avoiding errors.

I have illustrated my invention as embodied in an apparatusfor computing simple interest, and the table used in connection therewith is based on six per cent. per annum.

The apparatus consists, essentially, of a movable cylinder or support, upon the periphery of which is delineated a table constructed to show the interest upon one dollar at six per cent. for various periods of time and in tabular and progressive form the interest on multiples of one dollar for equal times. The table maybe extended to include any desired number of dollars within practicable limits, and in order to enable this extension to be conveniently made I may employ a plurality of cylinders or other devices, whereby extended surfaces may be provided and brought into convenient position, so that the characters thereon may be read. These cylinders, supports, or carriers for the table are used in combination with a sliding decimal-bar arranged transversely of the columnsand parallel with the rows of figures therein, this decimal-bar having a series of pointers thereon, one for each period of time, each such period having its appropriate column, and by shifting this bar, with its pointers, the value of the numbers under each heading may be increased or diminished in a tenfold ratio, the pointers indicating the carrying or removal of the decimal-point to the right or left, as the case may be. In order to still further multiply the power of the apparatus, each one of these pointers is made independently movable, being preferably pivoted between its ends, and by its move ment made to expose a figure or character indicating an additional period of time and also moving the decimal-point, thus introducing an additional multiplication or division of the amount in question.

In the accompanying drawings, Figure 1 is a front elevation of an apparatus embodying my improvements, a central section thereof being broken out. Fig. 2 is a perspective view of the decimal-bar and its pointers and a portion of the cylinder. Fig. 3 is an end elevation of the apparatus. Figs. at and 5 are sectional views showing a modified construction wherein a plurality of cylinders or table-supports are employed, and Fig. 6 is a detail of a locking-bolt.

In the drawings let 10 represent a casing having a hinged cover 11.

12 represents a shelf carried by the front of the casing, said shelf having in its upper surface a grooved way, in which slides a decimalbarl3. Said bar may be a fiat plate of metal confined within the ways by means of the headed screws 1.4, whose shanks pass through slots 15 of the bar. A tooth 1G is secured to the under side of the bar and is engaged by the gear-teeth 17 on a short shaft 18, having a milled head. Pivotally mounted upon said sliding bar are a series of pointers 19. The rear ends of these pointers, behind their pivots, work beneath a cover-plate 20, the latter having segmental slots 21 therein, while upon the upper surfaces of the rear ends of the pointers numbers are delineated. These numbers, as I have shown them, may be arranged in series from 1 to 30, inclusive,with two ciphers annexed to each number. These numbers represent timestand for days-while at the extreme right of the machine I have repeated the numbers 100. and 200, said numbers representing years. The extremities of the pointers have thumb-pieces 22, by which they may be moved upon their pivots. On the front of the casing are arranged a series of sliding shutters 23, whose lower ends depend below the plane of the pointers, so as to cut off the view of the numbers. WVithin the casing is mounted one or more revoluble cylinders. As arranged in Figs. 1, 2, and 3 a single cylinder only is employed, (marked 24.) This cylinder is journaled in the end walls of the casing, and its journals have operating-knobs or hand-wheels 25, one of which may have a series of arms 26, provided with the indicator-buttons 27, marked With a certain relation to the numbers applied to the cylinder 24L.

Upon the peripheryof the cylinder may be delineated in the first column, or at the lefthand side of the machine, a series of numbers commencing with 1 and extending to the capacity of the cylinder, preferably dropping out the numbers expressed by even tens. Each of these numbers will have affixed thereto by preference a series of ciphers. For example, the first number appearing on the cylinder will be 1, succeeded by five or six ciphers, so that assuming the decimal-point to be moved with relation to this number it may be made to express 10, 100, 1,000, &c., up to 100,000. In the next row in the same column the figure 2 will appear, followed byfive ciphers, and so on to the end of the column. By calculation the interest on the amounts represented by the digits in the first column is computed for the several periods of time represented in succeeding columns and the results appropriately placed. The time will be represented most conveniently in days, up to thirty days, or one month, and then the computation may be made in months, days, or years, as desired.

Let it be assumed now that the interest is required on seven hundred and twenty dollars. The cylinder will be turned until the number 7 2 appears. The decimal-barwill be shifted so that the fixed pointer 28, carried thereby, will point off from the number the three figures on the left-namely, 720. The shifting of the decimal-bar to include these three figures will carry the several pointers representing time to corresponding positions below the numbers representing the interest computed for those times. Thus the interest for one day will be twelve cents; for two days, twenty-four cents; for thirty days, three dollars and sixty cents; for one year, forty-three dollars and twenty cents, and for two years, eighty-six dollars and forty cents. But suppose the interest is required for seventy days. Then the pointer for indicating seven days time is swung upon its pivot to expose a cipher following the number 7 on the pointer, and seventy days is thus read, while at the same time the extremity or tip of the pointer has moved one place to the right, thus effecting the multiplication of the former interest by ten, and reading from the table we find that the interest for seventy days is eight dollars and forty cents, or ten times eightyfour cents, the interest for seven days. Thus bya single operation and observation the interest may be ascertained for any number of days from one to thirty, inclusive, upon the said principal, and by swinging any one of the pointers upon its pivot the time and the amount of interest may be multiplied tenfold, one hundredfold, &c., according to the number of ciphers employed. Of course the multiplication of the interest tenfold is equivalent to the multiplication of the time tenfold, and the operation may be expressed or explained by reference either to time or amount of interest. For any number of days exceeding thirty and represented by a number ending in a significant figure the interest would be found for the nearest number of days ending with a cipher, and then the number of days in excess thereof would be shown by observing the amount opposite the pointer corresponding to that number and the two sums added to obtain the total interest. Thus for two hundred and twenty-nine days the pointer bearing the number 22 followed by two ciphers would be shifted to expose one cipher, and the number of days would read 220, and the pointer would indicate twenty-six dollars and forty cents, while the pointer marked 0 would indicate one dollar and eight cents, and the sum of these amounts, or twenty-seven dollars and fortyeight cents, would represent the interest for the required time. Now if it was desired to find the interest on seven thousand two hundred dollars the decimal-bar would be shifted to the right to include an additional cipher.

I have shown the shutters as being capable of sliding movement and normally so disposed as to conceal all of the tabulation work upon the cylinder; but it may be desired to expose an entire row of numbers simultaneously, particularlyif the computation require the reading and addition of two sums to find the interest for the required time. To enable all of the shutters to be raised and lowered simultaneously, they may be mounted upon the sliding plate 20, having rack-bars 30, in which are engaged small pinions 31 on the operating-rod 32, the latter extending longitudinally through the casing and being provided with milled heads 33 on its ends exterior to the casing.

In Figs. 4: and 5 I have shown an apparatus having an increased capacity, due to the pro vision of a series of cylinders 3st, each mo unted so as to be independently rotatable upon its axis and carried by the spider heads or arms 35 of an external cylinder 36. Each of the cylinders 34 has a gear-whcel 37 upon one of its journals, and all of said gear-wheels are enmeshed with a central gear 38 on a shaft 30, passing through the hollow trunnion of the external cylinder. Shaft 39 and hollow trunnion 40 are provided with the handwheels 41 42, respectively, by means whereof the external cylinder may be rotated to bring any row of numbers placed upon its periphery into convenient relation to the decimal-bar and also so as to carry any one of the internal cylinders to the same point. The external cylinder has longitudinal slots 43 in its body, and through these slots numbers delineated upon the internal cylinders may be seen, and by the manipulation of the shaft 39 any one of said internal cylinders may be rotated upon its axis, so as to bring any row of numbers thereon into proper position with relation to the sight opening. When a number is to be read from one of the internal cylinders, the outer cylinder will be locked by the sliding locking-bolt 44, carried upon'the lever 45, backed up by the spring 46 and controlled by the sliding stem 47, having a head or button 48, whereby the spring 46 may be overcome and the locking-bolt held normally released by the spring-latch 49. By employing a plurality of cylinders the surface or area for the delineation of numbers is materially increased Without increasing the size of the apparatus, and thus the capacity of the apparatus may be enlarged and made adequate to a vast range of. computations.

While thus the capacity of the machine may be very much enlarged, it may also be found desirable to materially reduce its capacity. For example, suppose that the apparatus was required for use in savings-banks, where the only variable quantity or factor in the computation is the principal on which the interest is to be computed, the rate and time being fixed either by statute or the rules of the bank. The number of deposits in a single savings-bank may be very great, and the interest according to the general practice is computed at a fixed rate for even periods of time on all accounts of the same class. Therefore the only requirement would be a movable table upon which could be delineated amounts ranging from one dollar to the limit of savings accounts, while a single column would represent the computation of interest for the period, and a third column might con tain the amount of the principal plus the interest for the given time. Thus three parallel columns and a decimal-bar containing only three pointers would be required, and instead of the long cylinder shown a very short cylinder and a compact and inexpensive apparatus could be provided for.

Where a considerable range of numbers is required to be operated upon-for example, more than could be placed upon a single cylinder of convenient diameter-instead of employing a plurality of cylinders the same result could be accomplished by placing different sections of the table adjacent to each other upon a single cylinder, and the manipulation would be more simple than that required in a machine employing such plurality of cylinders. Of course instead of the cylinder holders of other kinds, such as flexible curtains or the like, might be substituted to receive the tables.

The foregoing description contemplates the calculation of interest at a uniform rate; but

in some banking institutions different rates of interest are paid upon different classes of accounts, and therefore it may be found expedient to embody in the same apparatus (which may be of either of the forms above indicated) tables computed at the several current rates of interest.

The two chief advantages of my invention will, it is believed, be found to reside,- first, in the fact that computations may be more rapidly made, and, second, that accuracy and the avoidance of errors will be insured.

I make no claim in the present application to the subject-matter set forth in two concurrent applications filed by me of even date herewith for Improvements in arithmetical calculators, serially numbered, respectively, 657,770 and 657,780, in the latter of which I have claimed in substance an arithmetical calculator comprising a suitable backing or support having numbers thereon and a decimal-bar having fixed pointers, said support and said bar and pointers being capable of relative movement, while in the former of said applications I have claimed a similar structure comprising a plurality of cylinders or supports having numbers thereon and a decimal-bar having pointers, said supports being rotatable upon their own axes and bodily movable.

I claim 1. An interest calculator comprising in combination an interest-table delineated upon a suitable support and comprising, in parallel columns, numbers representing the principal and numbers representing the interest calcu* lated for various times and a decimal bar or indicator, said table and said barbeing movable with relation to each other and said deci mal-bar having pivoted pointers, substantially as described.

2. An interest -calculator comprising in combination an interest-table mounted upon a suitable backing or support, a bar having pointers thereomsaid bar and said table being movable with relation to each other, whereby Various amounts may be indicated, and said pointers having each an independent movement, whereby multiplication of one of the factors may be mechanically effected, sub stantially as described.

3. An interest calculator comprising in combination a rotatable cylinder or support having delineated thereon, in parallel columns, numbers indicating principal and interest, a bar having pointers thereon, one for the principal and one for each of the several columns representing interest or time, said pointers being pivoted upon said bar and serially numbered, said serial numbers having each arranged adjacent thereto, one or more ciphers normally concealed and capable of being exposed by the manipulation of the pointer, whereby the time indicated by any given pointer may be increased and the interest correspondingly increased by such manipulation, substantially as described.

4. An interestcalculator comprising in combination a rotatable support or cylinder adapted to receive thereon an interest-table, a sliding decimal-bar having pointers pivoted thereon, said pointers being serially numupon a common support capable of bodily 1o beredandaseries ofmovable shutters, Wheremovement, whereby said shutters may be by any number delineated upon the cylinder separately or simultaneously moved as demay be separately exposed, substantially as sired, substantially as described. 5 described. a y T 1 5. In an interest-calculator, the c'ombina- VARRILN DRARP tion with a rotatable cylinder or support, of a lVitn'essesi b V sliding decimal-bar having pivoted pointers FREDERICK C. Goo'owIN, and a series of movable shutters mounted T. MANN. 

